Excel function menus unavailable in IE

[DJ]

This may also be an IE 6 problem.

Running Win2K SP4, IE 6 SP1, Excel 2000 SP3

Strange problem I have noticed on one of my machines. When
I open up a spreadsheet in IE the menus for Excel-related
items do not work or even open even though they are
visible. If I right-click a cell, Excel-specific options
are available.
On another machine this works.

Tried so far-
Re-registering Excel
Re-installing IE
Re-installing MS Office

TIA!